1. Field of the Invention
The present invention relates to a semiconductor device manufacturing method using an electrostatic chuck and a semiconductor device manufacturing system in which this method is applied, and particularly to a semiconductor manufacturing method including a step of applying a voltage to an electrostatic chuck which is placed in a process chamber in order to hold a substrate to be processed, and a semiconductor manufacturing system in which the foregoing method is applied.
2. Description of the Related Art
There is known a semiconductor manufacturing system in which an electrostatic chuck is placed on a substrate stand in a process chamber, and a substrate to be processed is processed while it is stuck onto the electrostatic chuck. The electrostatic chuck is constituted by a conductive layer and insulating layers covering the opposite surfaces of the conductive layer. The conductive layer is a thin copper (Cu) film or a thin tungsten (W) film or the like. The insulating layers are polyimid insulator sheets or ceramic insulator sheets or the like. With this electrostatic chuck, a DC voltage is applied to the conductive layer in order to induce electric charge on the insulating layer between the conductive layer and the substrate and to stick the substrate onto the electrostatic chuck using static electricity.
Two types of electrostatic chucks are available at present. One of them is a mono pole type electrostatic chuck including a flat conductive layer whose shape is identical to a substrate to be processed. The other is a multi pole type electrostatic chuck having a conductive layer divided into a plurality of flat parts which are shaped identical to the substrate, and are applied DC voltages having different polarities.
A semiconductor device is manufactured by a manufacturing system including the foregoing electrostatic chuck, in the following manner.
(1) First of all, a DC voltage is applied to the electrostatic chuck placed on a substrate stand in a process chamber. The substrate stand also functions as a processing electrode. Alternatively, a processing electrode is provided on the substrate stand. Because of the applied DC voltage, electric charges are accumulated on the surface of the electrostatic chuck.
(2) In this state, a substrate to be processed is brought on the electrostatic chuck and is stuck onto it. The substrate is a semiconductor wafer made of single crystal silicon (Si), for example.
(3) A process gas is introduced into the process chamber. Pressure inside the process chamber is appropriately controlled to a predetermined value. In this state, a high frequency power or the like is applied to the processing electrode, thereby generating discharge plasma in the process chamber.
(4) The surface of the substrate or a particular thin film formed on the surface of the substrate is processed as predetermined by the process gas introduced into the process chamber or discharge plasma generated in the process chamber. In this case, the thin film on the substrate is etched, or a further thin film is formed on the thin film of the substrate.
(5) Thereafter, introduction of the process gas is stopped, generation of discharge plasma is suspended, and application of the DC voltage to the electrostatic chuck is stopped.
(6) The processed substrate is released from the electrostatic chuck, and is taken out of the process chamber.
The foregoing process seems to suffer from the following problems. A positive voltage with respect to the ground potential is applied to the conductive layer of the mono pole type electrostatic chuck. Then, the substrate to be processed is stuck onto the electrostatic chuck in order to prevent the substrate from slipping or being displaced on the substrate stand, or the like. When the DC voltage is applied to the electrostatic chuck, positive charges are induced on the electrostatic chuck. Since particles present in the process chamber are usually charged to a negative voltage, they are attracted onto the surface of the electrostatic chuck. Positive charges are also induced on the surface of the substrate stuck onto the electrostatic chuck, which means that particles are also attracted onto the substrate. If dry etching is performed in this state, particles on the substrate serve as an etching mask. As a result, the substrate cannot be dry-etched as desired, and are not usable, which means reduced yield of manufactured semiconductor devices.
This kind of problem is also present in the CVD (chemical vapor deposition), sputtering and so on in which plasma is used.